This invention relates broadly to low-friction, movable, rocket nozzles. More specifically, it relates to such nozzles having a compliant bearing seal that remains effective despite temporary deformations of the nozzle members. The invention herein described was made in the course of or under Contract No. F04611-75-C-0063 with the U.S. Air Force.
Movable thrust nozzles have proved to be the most successful means for steering rockets. However, considerable difficulty has been presented by the fact that such nozzles must incorporate gastight seals capable of containing flaming, erosive gases under very high pressures and still be movable by light weight equipment over a practical deflection angle.
Spherical, metal-to-metal surfaces have been used for joining the parts of movable rocket nozzles, sometimes supported by gimbal mechanisms and sealed together with elastomeric rings. Such nozzles require high precision, and sometimes galling between the metal surfaces becomes a problem. More recently, elastomeric bearings made of laminae of metal and elastomer alternately stacked and bonded together have been used to support the movable portion of the nozzle relative to the portion that is fixed to the rocket. Such bearings have been successful in effecting gastight seals while providing the capability of relative motion. However, considerable torque is necessary to deflect the movable member of the rocket. Moreover, elastomeric bearings possess some of the properties of springs and resist being moved out of their neutral positions. This resistance is roughly proportional to the deflection angle, so that increasing force is required to move the nozzle as the deflection angle increases.
The present invention, which overcomes some of these difficulties of the prior art nozzles, is essentially a thrust-vectoring, rocket nozzle having an annular, lubricous, bearing pad between the bearing surfaces of the movable and stationary members, that functions also as a gastight seal. It is bonded to the fixed member of the nozzle via a torsion ring and elastomeric pad. This not only permits a wide angle of deflection of the movable nozzle member, but also provides a low friction system that offers little resistance to actuators, so that the actuators also may be smaller and less powerful. Hence, the entire system saves considerable weight that may be used more profitably to increase the payload and/or range of the rocket. At the same time, the lowered friction promotes faster responsiveness.
The bearing pad is made of woven fibers of lubricous material, that may be reinforced on the side bonded to the torsion ring by weaving refractory, high tensile strength fibers into those of the lubricous material or by bonding a thin sheet of refractory material to one side of the pad. Interstices between the fibers of lubricous material are filled with the same material or with other resinous material, so that it forms a gastight seal.
The present invention provides an improvement over that of the related application cited above. That application describes an annular pad of lubricous material rigidly fixed to either the ball or socket portion of ball-and-socket type of movable rocket nozzle. This pad functioned, as does that of the present invention, for the simultaneous, dual purpose of providing a low-friction bearing and a gastight seal capable of containing the hot, propulsive gases of the rocket.
A difficulty with the prior invention, however, is that, since the bearing pad is thin and is bonded directly to a nozzle part, considerable precision is necessary in manufacture of the parts in order for the bearing pad to function also as a hot gas seal. Such dimensional precision increases the cost of the nozzle. Hence, it is desirable that the dimensional tolerances be less limited.